This invention relates to.acid-dyeable polyester compositions suitable for use in manufacturing fibers, fabrics, films and other useful articles, the articles, and methods of making such compositions and articles. The acid-dyeable polyester compositions contain a polymeric additive composition that has secondary nitrogen groups. The secondary nitrogen groups provide improved acid dyeability. This invention also relates to the polymeric additive composition.
Polyesters, especially polyalkylene terephthalates, have excellent physical and chemical properties and have been widely used for resins, films and fibers. In particular, polyester fibers have a high melting point, and can attain high orientation and crystallinity. Accordingly, polyesters have excellent fiber properties such as chemical, heat and light stability, and high strength. However, polyesters, especially polyester fibers and fabrics, are difficult to dye. The molecular structure and the high levels of orientation and crystallinity that impart the desirable properties to the polyester also contribute to a resistance to coloration by dye compounds. Also contributing to the difficulty in dyeing polyester compositions is the characteristic that polyesters do not have dye sites within the polymer chain that are reactive to basic or acid dye compounds.
Blending of nylon 6 or nylon 6,6 with polyester has been proposed to obtain the benefits of the polyamide acid dye sites in the resulting composition. The high concentrations of polyamide that may be required to impart dyeability in the resulting polyester/polyamide copolymer composition result in decreased physical properties in the polyester/polyamide copolymer and difficulties in processing. For example, Canadian Patent No. 974340 discloses an acid-dyeable polyester composition using polyamides having cyclic, tertiary nitrogen-groups incorporated into polyalkylene terephthalates by blending and extruding the two polymers, and reports that polyamide microfibrils form within the polyester matrix during filament extrusion operations when high polyamide concentrations are used.
Commonly assigned U.S. Pat. Nos. 3,901,853, 4,001,189 and 4,001,190 disclose that many methods have been proposed for improving the acid-dyeability of polyester fibers and filaments by co-polymerization of nitrogen containing modifiers into the chains of polyester molecules, but that they have been inadequate for various reasons. U.S. Pat. Nos. 3,901,853, 4,001,189 and 4,001,190 further disclose that in order to provide good acid-dyeability, the modifier should contain a highly basic nitrogen atom that functions as a dye site but does not adversely affect molecular weight or cause discoloration. Thermal stability, effectiveness at low concentrations and low volatility are important properties of the cyclic, tertiary 2,2,6,6 tetramethylpiperidine groups that are disclosed as nitrogen containing modifiers.
U.S. Pat. No. 3,867,478 discloses that the use of polyamides containing tertiary amino groups in polyesters results in brown, discolored fibers after melt-blending and melt-spinning. The brightness of the dyed fibers is also reported as reduced. U.S. Pat. No. 3,867,478 discloses the use of phosphorus compounds to improve the dyeability of polyesters containing tertiary amino groups.
Japanese Kokai No. 47-32184 discloses that nitrogen containing polyesters are difficult to acid-dye because the addition of sufficient nitrogen dye sites into the polymer causes coloring in the polymer and decreases physical properties. Lower amounts of basic nitrogen in polyesters are said to be insufficient to develop adsorption toward the acidic dye. The addition of benzene derivatives to the dye bath is proposed to improve the dyeability of the fibers.
Although, as described above, substantial work has been done with respect to the use of tertiary amine compounds to enhance the dyeability of polyesters, secondary aliphatic amines have generally been used in polymeric compositions as chain branching agents or crosslinkers because of their functionality. U.S. Pat. No. 4,145,473 to Samuelson, et al. discloses the use of bis-(hexamethylene)triamine as a branching agent to increase the viscosity of polymer compositions used in melt spinning fibers.
U.S. Pat. No. 5,068,283 discloses a method for producing a thermoplastic resin wherein a saturated polyester resin and an epoxy group-containing ethylene copolymer are melt-kneaded into a composition and then further melt kneaded with a polyfunctional compound which carries out a partial cross-linking reaction. The polyfunctional compounds may be an amine. However, as disclosed in U.S. Pat. No. 5,322,923, the presence of structural derivatives of bis-(hexamethylene)triamine in amounts greater than 0.5 weight % has been shown to cause an undesirable increase in the viscosity characteristics of copolyamides used as molding compositions.
Methods that relate to treating a polyester with a dye composition containing nitrogen compounds, as opposed to including a nitrogen containing additive in the polyester, have also been proposed. U.S. Pat. No. 3,932,126 discloses a process for acid dyeing shaped or preformed polyester materials by applying an aqueous solution or printing paste of one or more acid dyes, various organic nitrogen compounds and organic carboxylic acids. The impregnated polyester material is dried and then heated. The preferred organic nitrogen compounds include alkyleneamines, alkanolamines and alkylamines.
All of the aforementioned documents are incorporated herein by reference.
It is desirable to have acid-dyeable nitrogen-containing polyester compositions which may be easily processed into fibers, films or other shaped articles and acid-dyed without expensive additives, special solutions, and/or complicated application procedures.
This invention is directed to an acid-dyeable polyester composition comprising (a) polyester and (b) secondary amine or secondary amine salt in an amount effective to promote acid-dyeability.
Preferably the acid-dyeable polyester composition is prepared by melt blending (a) polyester; and (b) polymeric additive prepared from (i) triamine containing secondary amine or secondary amine salt unit(s) and (ii) one or more other monomer and/or polymer units.
In another preferred embodiment, the acid-dyeable polyester composition of claim 1 prepared by melt blending (a) a polyester; and (b) a polyamide or polyamide salt selected from the group consisting of poly-imino-bisalkylene-terephthalamide, -isophthalamide and -1,6-naphthalamide and salts thereof.
By xe2x80x9cpolyesterxe2x80x9d or xe2x80x9ca polyesterxe2x80x9d applicant is referring to single polyester, or blends or mixtures of polyesters. This comment also applies to xe2x80x9cpolymeric additivexe2x80x9d, xe2x80x9cpolyamidexe2x80x9d, xe2x80x9cpolyamide saltxe2x80x9d, and other such terms that are used herein. Thus, for instance, if applicant refers to a composition containing X mole % of a polyester, the composition may comprise X mole % of one polyester or X mole % total of different polyesters.
The polyester is selected from the group consisting of polyalkylene terephthalate, polyalkylene naphthalate and polyalkylene isophthalate.
Preferably the acid-dyeable polyester composition comprises at least about 0.5 mole %, more preferably at least about 1 mole %, most preferably at least about 2 mole %, of secondary amine units. Preferably the acid-dyeable polyester composition comprises less than about 15 mole %, more preferably less than about 10 mole %, and most preferably less than about 5 mole % of secondary amine units. This mole percentage is calculated based upon the number of repeat units in the polyester composition, including the polyester and polymeric additive.
Preferably the polyester is selected from the group consisting of polyethylene terephthalate, polytrimethylene terephthalate and polytetramethylene terephthalate, more preferably polytrimethylene terephthalate.
The polyamide comprises a compound having the following formula: 
Preferably A or B, which may be the same or different, are selected from aliphatic or aromatic substituents.
Preferably n is at least 3, more preferably at least 10. Preferably n is 30 or less, more preferably 20 or less. Most preferably n is 15.
Preferably a is at least 1, more preferably at least 3, most preferably at least 5. Preferably a is 20 or less, more preferably 12 or less.
Preferably b is at least 1, more preferably at least 3, most preferably at least 5. Preferably b is 20 or less, more preferably 12 or less.
Most preferably, A or B, which may be the same or different, are selected from alkyl and aryl and each may contain 0-20 alkyl units and 0-3 aryl units, provided that each contains at least one aryl unit or at least two alkyl units. The alkyl and aryl units may be substituted or unsubstituted, straight or branched, etc., as long as the substituent(s) and branches don""t substantially interfere with dyeing or other fiber properties (e.g., the chain may contain an ether group).
Preferably the polyamide is poly(6,6xe2x80x2-imino-bishexamethylene terephthalamide) having repeat units according to the formula: 
wherein n is preferably at least 3, and n is preferably 30 or less.
The polyester composition may be in the form of a fiber, such as a monocomponent or bicomponent fiber, or a yam made therefrom. The polyester composition may alternatively be in the form of a film or film layer.
In one preferred embodiment, the polyester composition comprises a block copolymer of the polyester and the polymeric additive. By block copolymer, for example with reference to the poly(6,6xe2x80x2-imino-bishexamethylene terephthalamide) polymeric additive and polytrimethylene terephthalate, applicants are referring to a polymer formed by the polyester joined to the polymeric additive by a covalent bond.
The invention is further directed to an acid-dyed polyester composition prepared by acid dyeing the composition described above, and a process comprising (1) providing the polyester composition and (2) acid dyeing the composition. When the polymeric composition comprises a triamine containing secondary amine unit(s), the primary dye site is the imine thereof.
The invention is also directed to a blend comprising (a) polyester; and (b) polymeric additive prepared from (i) triamine containing secondary amine unit(s) or secondary amine salt unit(s) and (ii) one or more other monomer and/or polymer units or a salt thereof. Alternatively, it is also directed to a blend comprising (a) polyester; and (b) polyamide or polyamide salt selected from the group consisting of poly-imino-bisalkylene-terephthalamide, -isophthalamide and -1,6-naphthalamide and salts thereof.
In addition, the invention is directed to a compound having the following formula: 
A or B, which may be the same or different, n, a and b are preferably as described herein.
The invention is also directed to a process for preparing an acid dyeable polyester composition comprising the steps of (1) combining about 0.5 mole %-about 15 mole %, or the preferred amounts specified herein, of secondary amine units with a polyalkylene terephthalate, polyalkylene naphthalate or polyalkylene isophthalate in a polymeric additive wherein the amount of secondary amine units is effective to promote acid-dyeability, (2) mixing and heating the polymeric additive and said polyalkylene terephthalate at a temperature sufficient to form a blend, and (3) forming the blend into a shaped article.
In one embodiment, the invention provides an acid-dyeable polyester composition comprising at least about 50 and up to about 99.5 mole % of a polyalkylene terephthalate, and from about 0.5 mole % -about 15 mole % of secondary amine units in a polymeric additive. (Mole percentages are based on the repeat units in the polyester composition.) This amount of secondary amine units is effective to promote acid-dyeability. Where the secondary amine units form part of a polymeric additive, the comonomer will also be present in about 0.5 mole % -about 15 mole %. The amount of secondary amine units effective to promote acid-dyeability is preferably at least about 0.5 mole %, more preferably at least about 1 mole %, most preferably at least about 2 mole %, based on the polyester composition. The amount of secondary amine units effective to promote acid-dyeability is preferably about 15 mole % or less, more preferably about 5 mole % or less, based on the polyester composition.
In preferred embodiments of the invention, the polymeric additive may comprise secondary amine units combined in substantially 1:1 molar ratio with other monomer units, for example terephthalate or naphthalene dicarboxylate units, in order to construct the polymeric additive in such a way that it may be easily combined with polyesters such as polyalkylene terephthalate.
The secondary amine unit may preferably be obtained from a compound selected from the group represented by H2N(CH2)mNH(CH2)nNH2 and its salts with a phosphorus-containing acid. Therein, m and n, which may be the same or different, are integers, preferably at least two, more preferably at least 4, preferably ten or less and preferably eight or less. The secondary amine unit may be an unsalinized amine, or may be partly or completely salinized with a phosphorus-containing acid such as phosphorous acid, phosphoric acid or pyrophosphoric acid. Preferably the amine is bis(hexamethylene)triamine (m=n=6), and preferably it is combined with a terephthalate or naphthalene dicarboxylate unit. Preferably the polyalkylene terephthalate polyester is polytrimethylene terephthalate. In embodiments of the invention, the acid-dyeable polyester composition of the invention is a block copolymer of polyalkylene terephthalate and a polymeric additive comprising secondary amine units and terephthalamide or naphthylene dicarboxylamide units in substantially 1:1 molar ratio.
The invention provides an acid-dyeable polyester composition that may be shaped into fibers, films, membranes and other useful shapes and is easily acid dyed to a dye exhaustion of about 30%-about 80% or higher, preferably about 60%-about 80% or higher.
The invention also provides a process for preparing an acid-dyeable polyester composition comprising the steps of: (1) combining secondary amine units with polyalkylene terephthalate in polymeric additive wherein the amount of secondary amine units is effective to promote acid-dyeability; (2) mixing and heating the polymeric additive and the polyalkylene terephthalate at a temperature sufficient to form a blend, and (3) forming the blend into a shaped article.
The term xe2x80x9cblendxe2x80x9d as used herein to describe a composition is taken to mean a composition comprising a copolymer of the polyalkylene terephthalate and the polymeric additive, which may also include unreacted polyalkylene terephthalate and/or unreacted polymeric additive. The blend may comprise at least about 70%, more preferably at least about 80%, and most preferably at least about 90%, of a copolymer of the polyalkylene terephthalate and the polymeric additive. Most preferably, the blend comprises at least 90% of a block copolymer of the polyalkylene terephthalate and the polymeric additive. The shaped articles may be stretched and heat treated to develop physical properties either before or after treatment with acid dyes.